The present invention relates to a seat belt pretensioner for a vehicle. More particularly, the seat belt pretensioner for a vehicle includes a spool, onto which a seat belt is wound, wherein the spool is moved downward at the onset of an accident by means of an explosive force.
A vehicle seat belt is a crucial part of a vehicle""s safety components. Seat belts assist in securing the safety of the driver and passengers at the onset of a crash and have become a mandatory feature for vehicles. Seat belts, once fastened, preferably do not create unnecessary discomfort for a driver nor restrict too tightly the body of a driver and passengers, thus minimizing bodily damage incurred during car accidents. One important feature of the seat belt is the seat belt pretensioner. Pretensioners often use an explosive force in activation to tighten the seat belt a prescribed amount during firing of the explosive force. The pretensioner is often positioned on the retractor which is wound up by the elastic support of a seat belt.
FIG. 3a shows the structure of a conventional pretensioner. In this configuration, a clutch 110 is mounted on a cover 100 and a seat belt is located at one end of a spool. The clutch rewinds the seat belt by rotating it in a reverse direction. The force for reversely rotating the seat belt if provided by a piston structure 120, which slides in response to an explosive force.
FIG. 3b shows the structure of another type of a conventional pretensioner. The structure of the pretensioner in FIG. 3b is such that one end of a spool, upon which a seat belt is wound up by the elastic support, protrudes outwardly from a position and a home gear 130 is mounted on the protruded end of the spool. A ball supply line 131 wraps around the home gear 130, thereby enabling the balls 132, which fill along the ball supply line 131, to reversely rotate the home gear 130.
FIG. 3c shows the structure of still another type of conventional pretensioner. The structure of the pretensioner in FIG. 3c is such that a seat belt extends from one end of a wound up spool 140. At the extended end a clamp wire 141 is installed. During an accident, an explosive force pulls the clamp wire 141 upwards, generating a frictional force which rotates the spool 140 inward.
FIG. 3d also shows the structure of another type of conventional pretensioner disclosed in U.S. Pat. No. 5,248,110. The structure of the pretensioner in FIG. 3d is such that a gear 150 is mounted on the spool 140 such that the gear 150 is rotated by the explosive force, thereby rotating the spool 140.
However, the spools in these conventional pretensioners have disadvantages in that they are forced to rotate and therefore the spool structures become rather complex and manufacturing costs become very high. Further, an enormous force is required to rotate the spool and wind up the belt.
The present invention provides a seat belt pretensioner for a vehicle wherein a spool is mounted in such a way that it cannot be further released at the onset of a car accident. However, the spool is pushed downward in a fixed state along a length-wise direction of a retractor and thus effectively partially rewind a seat belt when activated.
A seat belt pretensioner according to an embodiment of the present invention comprises a retractor cover wherein sliding guides are formed on both right and left sides. A spool is mounted in such a manner that a seat belt is wound up with an elastic support and is able to slide along a sliding guide. Furthermore a piston structure, mounted on the upper part of the cover, pushes the spool downwardly by an explosion force of explosives.
The sliding guides of the present invention are preferably mounted in parallel with the direction the seat belt is wound up or released.
The spool of the present invention is preferably equipped with a latch to prevent the release of a seat belt at the onset of a car accident.
The piston structure of the present invention preferably comprises an explosive powder chamber, which is mounted on the upper part of the cover and provides explosion gas to both left and right, and a pair of cylinders connected to said explosive powder chamber wherein each cylinder is positioned on the sides of the cover to be in parallel with the sliding guides, and wherein the internal end of each cylinder is connected to a spool.
According to another preferred embodiment of the invention, a seat belt pretensioner for a vehicle comprises a support member having a top and bottom, a seat belt spool having ends slideably supported by the support member, and a piston system acting on the spool to force the spool toward the bottom of the support member in response to a vehicle accident. Preferably, the support member comprises a retractor cover of a seat belt retractor mechanism. In a further preferred embodiment, a seat belt extends the spool in a predetermined orientation toward the spool ends, with the guide members being oriented at least substantially in parallel with the seat belt orientation. The piston system preferably comprises an explosive chamber, first and second cylinders communicating with the explosive chamber on opposite sides of the support member, and first and second pistons. Each piston is disposed in one cylinder and each is linked to an end of the spool. When an explosion is triggered in the explosive chamber, the explosive force communicates with the cylinders to act on the pistons to force the spool down, away from the extension of the seat belt.